Sedimentation Prototype Final Report
Introduction
Methods
Schematic
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Schematic of Apparatus Setup
Initial Apparatus Setup
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Initial Apparatus Setup
The initial apparatus set up was run by Process Controller which had functions set in place for when the system would turn on, off, or drain. It also included a pressure sensor that would control the flow rate of the system. It was found that the pressure sensor was unreliable and sensitive to changes in the environment. Additionally, the flocculator for this setup led to a high velocity gradient (G) of 129.1/s. This led to the formation of very small flocs.
New Apparatus Setup
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New Apparatus Setup
In the New Apparatus Setup the diameter of the flocculator was increased. This allowed for an increase in floc size and a significantly lower velocity gradient (G) of 35.7/s. Ideally, a G around 20/s is wanted, however, such a velocity gradient may have caused other important parameters to be too low. Additionally, the flow control system was changed to utilize a peristaltic pump allowing for a more stable system.
Design Parameters
Equations
Critical Settling Velocity
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Velocity Gradient
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Residence Time
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Length and Diameter Values
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Table 1: The data above shows length(L), diameter(D), and ratio of L/D values for each straw setup.
*The straw length was doubled because two straw packs were used in the sedimentation tank.
In regards to the length and diameter values, the table above shows a wide spread of L/D values. The no straws situation uses the measurements of the sedimentation tank. Additionally, in the case of the type 3 straw situation, the length of the 3mm diameter straws were significantly smaller than the other straws. To solve this issue, two packets of straws were used in the sedimentation tank so that the length for the 3mm straws could be doubled.
Critical Settling Velocity Values
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Table 2: The data above shows the critical settling velocities of each straw setup
Critical settling velocities demonstrate the shortest amount of time it takes for a particle to settle out. The Vc values above show how long it takes for particles to settle out in each straw setup situation. In comparison to the AguaClara plants which have a maximum critical velocity of 10 m/day, only the no straws situation exceeds this value.
Straw Bundles
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Type 1 Straws - 12mm
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Type 2 Straws - 5mm
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Type 3 Straws - 3mm
Results & Discussion
Matrix of Experiments
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Table 3: The data above is a matrix of the experiments performed for the Sedimentation Prototype.
As shown by the table above, 8 experiments total were performed.
Experiment Obstacles
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Floc Blanket
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Clogged Straws
Experimental Trials
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